1. Field of the Invention
The subject invention relates to systems for improving fuel economy and, more specifically, to methods and apparatus for assisting the driver of an automobile driven by an internal combustion engine to improve fuel economy with the aid of a device in the linkage coupling the accelerator pedal to the throttle valve and with the aid of the air intake manifold vacuum.
2. Description of the Prior Art
It has been known for some time that reading of the vacuum in the air intake manifold of an internal combustion engine can be used to improve fuel economy. To this end, major automobile manufacturers have started to offer a built-in vacuum indicator which measures and indicates to the driver the difference in pressure between the atmosphere outside the engine and the air inside the intake manifold. Further uses and refinement of such vacuum gauges have been described in Popular Science, March 1975, "Why Your Car Needs a Vacuum Gauge", pages 110 to 112.
In practice, there prior-art devices require driving "with one eye on the vacuum gauge", which is distractive to many drivers and thus tends to lead to accidents. Conversely, a conscientious driver who is paying attention to the road and the surrounding traffic situation is many times not in a position to observe the vacuum gauge. Moreover, special skills, experience and a high degree of calmness are required for an intelligent reading and use of a vacuum gauge during the operation of an automobile. Also, while such vacuum gauges will point to engine defects or maladjustments, they do not provide for a full utilization of the intake manifold vacuum condition throughout the course of normal driving with a well operating engine.
Prior-art efforts to provide vacuum-responsive engine control devices in the linkage between the accelerator pedal and the throttle valve have not led to a desired level of fuel economy.
In particular, the governor for internal combustion engines shown in U.S. Pat. No. 2,139,832, issued Dec. 13, 1938 to W. E. Leibing, had the disadvantage of introducing surges in the rate of rotation of the controlled engine. The vacuum controlling device shown in U.S. Pat. No. 2,627,850, issued Feb. 10, 1953, to R. Willim, in effect kept the vacuum in the air intake manifold at a minimum to increase horse power on acceleration.
The engine control system of U.S. Pat. No. 3,289,659, issued Dec. 6, 1966, to P. J. Koole, was impractical in its complexity and sensitivity to malfunction. A newer proposal, apparent from U.S. Pat. No. 3,769,951, by William H. Holl, issued Nov. 6, 1973, attempts to decrease undesirable exhaust emissions in response to sudden, jerky accelerator pedal actuation by nervous drivers, rather than concentrating on fuel economy as such.